Method of separating magnesium and calcium chlorides



Feb. 2, 1932. w. R, coLLlNGS 1,343,750

' METHOD 'oF SEPARATING MAGNESIUM AND cALcIuM oHLomnEs Filed Jan. 3l,1928 TACHYDE/TE' CES/5 TA ..5

ATTORNEY;

Patented Feb. 2, -1932 v WILLIAM It. .coLLINesonMIDLAND,MIoHIGANQssIeNoR 'roA 'Inn now CHEMICAL COMPANY, oF MIDLAND,MICHIGAN, Je,CeleronA'rIoN oF MICHIGAN v l METHOD onsEI'AnATiNe'MAeNEsIUMnNn CALCIUM' oHLonIDEs i, f iV Application? ineaJanuarysi, 192s;v sei-iai No. 250,822.

'l Yin UnitedStates .Letters-Patent N o. 1,62@-

068 to A. K. Smith andv C. F. Pruttomdated May 3, 1927, there-isdisclosed animproved method or process fortreating'brines which containcalcium and,v magnesiumf chlorides, withv the object of separating thelatter from each other. Incidentally to such process the calcium andmagnesium chlorides,at least in part, are crystallized out of thesolution in the form ofa doublesalt known 'as tachydrite('CaCl2-2MgCl2l-2I-I2O). These crystals-'rare then lseparated from ,theVmother liquor Vand 'by appropriate treatmetthe calciumwchlo.- ridecontent may be separated from` the mag-y nesium chlorideand the latterpurified. According to the process as described and claimed in theaforesaid Letters Patent, the separation of calcium chloride from thetachydrite is accomplished by agitat-ing the latterqwith Ya limitedquantity of Water` at regulated temperature to Ydissolve suchcalci'umlchloride constituent and leavey magnesiuml chloride, crystals behind. lSpecifically the tachydrite crystals arevmiXedwith about per cent; ofwater by weight andfagitated lin the vform of a thick slurryvforapproxi,- mately an hourat-a temperature which should not Vfall below 22degrees C.` nor rise above degrees C. Under these conditions `thewater'will causethe calcium chloride of the lution which when cooledtothe propertemperature will crystallize out magnesium chlorideinhexahydrate form j (MgCl2H2O),

the calcium chloride being retained in solution.

, 'More particularly'theinvention consists ofv improved process.

the steps hereinafter fullydescribedand'pan ticularly pointed out inAthe, claims, the annexeddlawingand the following descriptionyillustrating and setting forth' in detail certain steps embodying theinvention, vsuch disclosed"means constituting, however, but several ofthewa'ys in which vthe principle'fof the invention may be used. V

.In said annexed drawing-'r-y i The single figure there `appearinggrammatic representation on .the yorder-of a flow sheet illustrating theapparatus 'and steps employed in carrying out thefpresent So far as thevpresentV processisconcerned,

it is of course lamatter of indifference from isf a diafwhatvsource orin what manner the tachy- Y drite employedtherein is derived.VvIn'oth'er words, it Y need not .necessarilybe obtained from thenaturalbrine "such as the'Midland brine referred to inthe aforesaid Patent No.1,627,068. However, it Will be'gunderstood that where a natural brinejorone containing sodium chloride in additionlto the calcium and Vmagnesium'chlorides is employed, lthe sodiumk chloridel will .be irstsalt'ed youtfwell known meansY of concentration.

f According to-V the present: process, such tachydritel crystals aftersuch" preliminary steps, if any'be required, as may be deemed necessarytorwashorV otherwise purify the same, -arelentirely dissolvedlinalimited amount of water bythe addition of heat, such water. lbeingadded, at least in part, 'and 4the heat being supplied by injectingsteam into the mixture, and the Vtemperature being thus raised fromI 90degrees to 100 degrees C. However, the amount of Water'that is added isylimite'dvto jus't'enoughl so thatupon cooling theresulting solution toapproximately thereupon` are formed will be magnesium chloride in thelieXahydrate-form.' The magnesium chloride crystals thus obtained afterwashing contain `less than 0.5 per cent; ofcalcium chloride.'V vBy,entirely dissolvinglthe crystals opportunity is `also givenftojfilterpress Athe solution andth'us remove residual impurities suchasl'magnesium hydroxide,

:j 30 degrees C., all ofthe calciumch-loride will be inthe solution and'the cr'ystalswhich By Way' of:v aY more detailed description otv theprocedure vand having reterencetothe attached drawing', the t'achydrite,from Whatever source derived and afterrbeing Washed to remove as 'far aspossible adherent impuritiestronr thernotlier liquor, is dissolved inAa* suitable apparatus ll and the Asolution runA into a=storagctanlr 2.Froni'the latter rit is Witlidrawir'as required for use in the processthrough a-lter pressf' from'l which itI isA carried to ai crystallizer lWhere itv is cooled to' separate out magnesium chloride hexahydrate. Insummertime the solution may be precooledi iriaV vacuum cooler.5 beforefinal cool-ing in suchcry'stallizer in order to'mainta'in the capacityofv thelatt'er, als thoughv at Winter temperaturesthe solution may betransferred directly to suc-h crystallizer. The magnesiumhexahydrateacrystals and motherliquor are received inav lilter' 6,Where,-af'te1"separationof the mother liquor, thecrystafls-'may befurther Washed,.the lil'- trate and Wash- Wate'r being removed forreconcentratioir or for use otherwise as desired; The Washed crystalsfrom filter 6; are thenmelted tojproduce a1 strong magnesium chloridesolution which is" stored inv a tank 7 W'hencexit is transferred througha1 iilter pressS to another st'oragetank 9 and finallyn to'r thefinishing` kettle 10.y

The formationl of the dissolved tachydrite preliminarilytoitsstorageintankl and the tieatmentfo thefsolution incidentally to`its passz'ige-tor and through crystallizer 4l consti# tute thesteps-ofpart'icular interest in the presentlconnection. As previouslyindicated, such- .tachydrite is dissolved in a limited amountotlvv-adtera'ndY heatedup by blowing steam introy the mixture,y theapparatus in Whichgthis is accomplished consistingl preferably ot-a tankWithV a suitable stirrer and m'eansrfor thus injectingl steam into itscontents: YVVhen the temperature of the solution: in: the taule reaches90l degrees C., the

steami is shut off andV the strength of `the solution; adjusted. AnVamount of Water must be vadded such? that' When the solution iscooledg-the maximumlyield of puremagne- -sium chloride crystals isobtained. It too miichwater is added, the' yieldlot'magnesiumchlorideWillA be reduced, While if toolittle Iisaddedithecalcium'chloride'will not all be retained ini solution butwill" be crystallized inl part' along WithZ the maglie'siuln chloride inthetor'in ottachydr'ite crystals.v VThe condition of the solution canbest be measured by cooling` a. portion of it to 30 degrees C. andseparating the liquor from the crystals in a screen funnel. Experiencehas shown that it the gravity of the iiltrate is maintained between 425and 43 degrees B.,thefresulting magnesium chloride Wil-l' alWayYscontain less than V0.5 per cent. and usually less than 0.25 per cent.Vof calcium chloride after it is Washed Water is'then'ad'ded'to'the's'oliit'io'n 'until' tlie gravity of the'motherliquor is betweenthe above limits. a

The iltratioiiA received by the solution 1n assin f throuoh filter 6serves to remove P e small amounts of dirt,` hydrate, iron and residualsalt,V NaGl'. Where the vacuum cooler 5 is-f employed, it usually coolsthe liquor froinabout Tzdegrees@ to' degrees C., thereby raising; thevgrav-ity off'tllelsoluh tion approximately 2 degreesBeQaHd inz such casethe tachydrite solution shoud' be? corre'- spondingly adjusted@ i. ci,tof approximately el degrees B; when such vacuum cooler is in operation;In the' crystalllzerf 4i, Which .is preferably or" the SWensonLWalkertype; the mixture is cooled to i'omltof degrees C. lt 'isi aninterestingfact' that the' crystals Whiclrseparate outduring' the firstst'age ofthe' cooling: operationz are' t'achydritc; This taires place' until a itemperature? of abouty 50 degree C.' reached when magnesiumohloridecrystals start tosepar'at'e from theisolu# tion.V yAs the'coolingproceeds; megnes'ium cliloiidecrystals continuetolsep arat'eandlthe calcium chloride is redissolved fromjsiicli initially f'or'meditachydrite crystals; It is possible that the lattel" 'c'an be' said thredissolvc andrecrystallize; che calcium remain ing in solution:whilet'he: magnesium' chloride crystall-izi'es outA The' process, itshouldi beexplained,v isinot necessarily limited to starting withtachydritc crystals;l or' tachydritc asf su`ch,-.but thesolutionobtained therefrom andi stored in tank 2,/asf hcreinbcforcdescribed, i suclr solution containing magnesium; chloride and.I cal*Fciuni chloride in' approximately the' ratio l of two molecules ofthcforrner'tol cned` the latter, may be taken'as'the starting# point,irrespective of the specific manner'in which, or scurccfrom which; such.solutioir is derived; In fact, the methodI isl applicableVV to anysolutionof magnesiumf chloride and cal ciumchloride inE which the*molecular' ratio of" magnesium' chloride to calcium chloride is. greaterthan' approximately one' tof one, which latterY is the ratio ofmagnesium chloride; to calcium: chloride iii chemischer liquor"aft'e'rf' separation ofthe* magnesium chloride'clilicrystals; r

other moucsforapplying" ai@ principle cf the one explained, changebeingv madel as vregards the method herein disclosed, profollowingclaims or the equivalent of suchi stated step or steps be employed.

I therefore particularly point out and disi tinctly claim as myinvention l. The method of separating magnesium chloride from a solutioncontaining such chloride and calcium `chloride in a molecular ratiogreater than approximately one mole of the former to one of the'latter,Which comprises adjusting the amount of Water present to produce asolution at a temperature materially above 30 C. such that, When cooledt0 approximately 30 degrees C., the mother liquor remaining from thecrystals thereupon formed Will have a gravity of beween' l42.5 degreesand 48.0 degrees B.

2; The method of separating magneslum chloride from a solutioncontaining such chloride and calcium chloride in a molecular;

ratio greater than approximately one mole. of the former to one of thelatter which comprises adjusting the amount of water present at atemperature materially above 300 C. to produce a degree of concentrationsuch that When the solution is cooled to approximately 30 C. crystals ofMgClgI-IZO Will be precipitated and the mother liquor separated from thecrystals will have a gravity of between 425 and 43.0 degrees B., thencooling such solution to approximately 30 C. and filtering oil' thecrystals from the mother liquor containing the two chlorides inapproximately equimolecular ratio.

Signed by me, this 28day of January, 1928 i WILLIAM R. COLLINGS.

